1. Field of the Invention
The present invention relates to an electro-resistance element the resistance value of which changes by application of voltage or current, and to a method of manufacturing the same.
2. Related Background Art
Memory elements are used in a wide variety of fields as essential electronic components that are important to support today's information-driven society. In recent years, as portable information terminals have become increasingly popular, demands for miniaturization of memory elements have been increading, and non-volatile memory elements are no exception. However, as the scale of device miniaturization is approaching the nanometer range, a decrease in charge capacity C per information unit (bit) has become a problem with conventional charge storage type memory elements, typically DRAMs: Dynamic Random Access Memories. Although various improvements have been attempted to obviate this problem, there is a concern over the future technological limit.
As a memory element that is less prone to the adverse effects originating from miniaturization, a non-volatile memory element that records information by changes in electric resistance R, not by changes in charge capacity C, has attracted attention. As this kind of memory element, JP 2002-512439A discloses an element using a chalcogen compound (TeGeSb); U.S. Pat. No. 6,204,139 discloses an element using a perovskite oxide (Pr0.7Ca0.3MnO3: PCMO); and JP 2002-537627A discloses an element using various oxides including a perovskite oxide (see, for example, paragraph [0025]).
The element disclosed in JP 2002-512439A, however, utilizes a resistance change associated with a crystalline-amorphous phase change of the above-mentioned chalcogen compound, the element is also referred to as a phase change memory element, and the phase change of the chalcogen compound is controlled by applying heat to the element. In the phase change element, problems remain in miniaturization and response speed of the element.
The element disclosed in U.S. Pat. No. 6,204,139 has problems of stability in operation and reproducibility in characteristics. In addition, in order to construct a memory cell array with the use of the element, the element needs to be used in combination with a semiconductor element (a transistor, a diode, or the like) for selecting the element when recording and reading information, but crystallization of perovskite oxide such as PCMO generally requires a high temperature of from 650° C. to 850° C., leading to the problem of affinity with semiconductor manufacturing processes. In particular, in order to achieve high integration in memories associated with element miniaturization, it is desired that the manufacturing process temperature for the element be set lower than the just-noted temperature range.
JP 2002-537627A discloses an element employing various oxides including a perovskite oxide.
In addition to these prior examples, JP 2002-280542A may be mentioned as a prior example related to the present invention.
It is an object of the present invention to provide an electro-resistance element that has a different configuration from those of the conventional elements and is excellent in its resistance change characteristics. It is another object of the present invention to provide a method of manufacturing the element.